Nowadays, 3D imaging technologies experience great growth and are now rapidly gaining in popularity. Generally, the current 3D imaging technologies are divided into a 3D stereoscopic technology and a 3D autostereogram technology. For example, polarizing glasses and shutter glasses are commercialized products that comply with the 3D stereoscopic technology. Moreover, the commercialized products complying with the 3D autostereogram technology include for example a parallax barrier and a lenticular lens.
FIG. 1 schematically illustrates an imaging method for a conventional lenticular lens sheet. As shown in FIG. 1, the lenticular lens sheet 10 is composed of plural parallel elongated convex lenses 101. A synthetic image 12 is placed near a flat plane 102 of the lenticular lens sheet 10. For example, the synthetic image 12 is synthesized by portions of sub-image strips of two sub-images 121 and 122. That is, the odd-numbered portions of the sub-image 121 and the even-numbered portions of the sub-image 122 are interlaced with each other to constitute the synthetic image 12. Moreover, human eyes 14 are separated from a lens surface 104 of the lenticular lens sheet 10 by a certain distance. In a case that the synthetic image 12 is viewed through the lenticular lens sheet 10 by the human eyes 14, the 3D effect or the animation-like effect of the synthetic image 12 is viewable.
Generally, the parameters of the elongated convex lens 101 includes the angle, the pitch or period, the curvature radius of a lenticule, the thickness, the thickness of the substrate below the curved surface of a lens, and the refractive index of the lens. The viewing angle of the image that can be seen by the observer is related to the angle and the refractive index of the lens. In a case that the refractive index is fixed, the synthetic image 12 corresponding to the narrow-angle lenticular lens sheet 10 tends to have the 3D effect, but the synthetic image 12 corresponding to the wide-angle lenticular lens sheet 10 tends to have the dynamic effect.
Moreover, since the general lenticular lens sheet 10 only has the repeated curvature radius along the one-dimensional direction, the human eyes 14 are only able to watch the one-dimensional dynamic effect. Similar to the lenticular lens sheet 10, a lens array 25 composed of plural spherical lenses in an array is shown in FIG. 2. Since each of the spherical lenses has a 360-degree curvature, the 3D effect or the dynamic effect along multi-dimensional directions may be achieved.
However, since a precise mold is required to produce the spherical lens array, the fabricating cost is very high. In other words, the applications of the spherical lens array are restricted.